What does Team Birdwatch have left?
CR Stats used to do this sort of thing back in the day, and so I thought I'd try to write up what this group hasn't used yet.
The big one: Teor and Julien have yet to level up. This will grant them higher proficiency bonuses and more HP. Teor will get notably more powerful with the ability to summon a steed, take two attacks per turn, and he will get three more spell slots (one first level, two second level) even if Brennan doesn't let him take another spell right away; plus, five more Lay on Hands. Julien will either get cunning action (helpful for moving quickly or disengaging) or an ASI/Feat (big wildcard there) and a third use of Second Wind. However, this hasn't happened yet. It's safe to assume that unless they die too quickly (and frankly, if they're just knocked unconscious? I'd use that as a level-up opportunity if I were Brennan; I think it will have to be insta-kill) they will level up, but it's not in play yet.
The unknown: I don't know Cyd's statblock abilities beyond the fact that he can attack and he has Divine Sense that has not yet been used. He has lost 3 strength, and is down a net 33 HP from max.
With that said here's what L5 Thimble and Occtis and L4 Julien and Teor still have left in the tank. Of note: Teor's strength has been reduced by 4 and Julien's by 2. Teor's is more of a consideration as that's his attack stat whereas Julien is a dex fighter, but see below.
Occtis: At 22/37 HP. He has cast presumably Tenser's Floating Disc (in that he used it to get Gaya over to the manor); Detect Magic; Summon Undead; and Life Transference. This means he has used both 3rd level spells and two 1st level spells. He has two more 1st levels and all three 2nd level spells. Gaya as a Putrid Spirit from Summon Undead is still up, immune to necrotic damage, at 28/30 HP, and Occtis can command her as a free action on his turn, though this is a concentration spell and will only last an hour. Also, if they are able to get a short rest (risky, but might be worth it) he has Arcane Recovery and Memorize Spell, the former of which can get him one of his third levels back and the latter of which lets him swap out a prepped spell with one from his spellbook. I don't think he's used Unsettling Presence either; and if they encounter any non-undead he does have Grim Harvest for himself.
Thimble: At 42/53 HP. She actually has all of her main abilities intact - HP and the fact that a single shadow attack has a 50% chance of insta-killing her is the main concern at this point. As a fairy, she has one casting of Faerie Fire, which she hasn't used, and, upon hitting level 5, a casting of Enlarge/Reduce, which I think she could cast on others, for which Teor is probably the best bet. She also just got Uncanny Dodge (which uses a reaction) and Cunning Strike, which uses a sneak attack die but can be used to poison or trip enemies. Chances are damage will be better in this combat, but it's an option. Her sneak attack also just went up.
Teor: At 34/43 HP. He has used one of two usages of Channel Divinity on a Divine Sense. He's used all of his current Lay on Hands on Cyd, and he's used one spell slot (Guiding Bolt) of his three first levels. He has not used his free Divine Smite nor his Daunting Roar. His subclass permits him a Channel Divinity to augment his athletic abilities. He is also the only person to have used any Desperate Measures, having activated it to dash and disengage, so he has one marked death save fail. He will regain a Channel Divinity if they take a short rest. The other thing of note: it is unclear if he is attuned to the Bracers of Oak and Birch. If he is, his strength damage doesn't really matter, and he gets a casting of Barkskin. I suspect even if he's not now, he will attune during the level-up.
Julien: At 20/53 HP. He has not used Action Surge yet. He has used both Second Winds, one for Tactical Mind and one to grant himself temp HP with Ride the Threshold. Otherwise, he is a rogue/fighter with no spells. He would regain a Second Wind on a short rest. It's not clear how many times he can use the Hare's Charm per day or if there is a limitation.